Thermoforming (the process of heating and shaping synthetic material) is an increasingly popular way to utilize solid surface to create 3-D curves and rounded shapes. This is a realm where other surfacing materials like quartz and granite cannot be used. The ability to thermoform has made solid surface a favorite three dimensional artistic pallet for designers everywhere.
Start the process of shaping the solid surface material by heating it to the point that it becomes very flexible, much like a slice of fresh bread. Pay attention to the following factors when shaping the material into a radius or cylindrical shape:
- Material Preparation: cut the material slightly larger than the final dimension as it shrinks after heating. Prior to heating, the edges of the material must be sanded smooth with no chips, cracks or scratches. Small chips, cracks and scratches become the launching point for cracks to develop at a later time.
- Heating Solid Surface Material: it is best to heat the entire piece of material. If you heat a small section where the bend will occur, then there may be a tendency for stress to develop at the interface of the heated and not heated portions. The material needs to be heated to within a particular range of temperatures depending on the composition of the material.
- Material Flexibility: Acrylic material is the most flexible when it is heated to the appropriate temperature. A blend of acrylic and polyester is the next flexible, with an all-polyester material being the least flexible. (See the table below for temperatures and approximate times.)
- Heating: Be careful not to heat the material too much or too little. Under heating the material and then trying to form it can result in cracking, breaking or stretch marks. Overheating the material may cause it to bubble or blister. Heating the material may also cause it to darken in color.
- Bending and Shaping: After the material has reached the intended temperature, remove it from the oven and slowly bend it over or shape it into the desired form. If it is bent too rapidly, it may crack, break, or get white stretch marks. If bent too slowly, it may cool too soon. However, don’t worry, as there is generally sufficient time to get the heated material to the destination mold.
- Forms and Molds: Create a set of male and female molds from plywood or MDF for the material to be placed between while it cools. Let the material cool to below 170 degrees before removing.
- Imperfections: Forms and molds will transfer any imperfections contained in their surface to the material being thermoformed. One way to eliminate these markings is to line the surface of the mold with tempered hardboard (also known as peg board, but without the holes.)
- Conforming: If available, a vacuum membrane forming press can be used to help the material conform to the desired shape. At times, it is beneficial to use a “helper stick” or a shaped piece of wood to coax the material into position. Sprinkle of a light layer of talcum powder to make the process even easier.
- Cool Down: keep the material fixed in place until it reaches 180°F at the surface and then remove the restraints to allow the material to release stress. (NOTE: 180° is the temperature DuPont suggests for Corian®, other brands may vary.)
- Final Touches: Attend to seaming and other modifications after thermoforming is complete.
- Ovens: There are three styles of thermoforming ovens; infrared/radiant, hot air/convection, and platen press. The platen press oven is designed to come in contact with the sides of the material. This process consequently heats the material faster than the other two oven types. No matter what type of oven you decide to use to heat the material, make sure it is large enough to contain the entire piece. Calibrate the oven using the information from the “oven preparation section” of the Corian® Thermoforming Guide.